A compliant MCS is critical to the Worldwide Interoperability for Microwave Access (WiMAX) technology, to ensure the communication quality between a BS and a CPE. In the WiMAX-supported MCS, three modulation types exist, that is, Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (QAM) and 64 QAM. The BS may change the modulation mode according to the increase or decrease of a parameter CINR which is returned by the CPE and represents the communication quality.
However, in practice, one MCS is not adapted to the same CINR in all the channel environments between the BS and the CPE. The CINR is merely an averaged signal quality factor, so that it is inappropriate to select the MCS only according to the CINR in the actual channel environment. When the CINR is overestimated, the BS selects a high modulation and coding mode, which causes plenty of packet errors and reduces the transmission efficiency. In contrast, when the CINR is underestimated, a modulation and coding mode of a low transmission rate is adopted, which causes a waste of wireless resources.